Deputies couldn't find her at her main address or at a separate address that a local school system had for her.

Then two people -- the girl's grandmother and a Facebook employee -- called 911 to say the teen was at the grandmother's house in the city, which is roughly 80 miles south of Atlanta, Howard said. Someone had told the grandmother, who was not at home, about the Facebook stream.

Facebook users can alert the social network to alarming videos, but Howard didn't say how the Facebook worker who called learned about this incident. Facebook spokeswoman Andrea Saul declined to comment on this case, citing privacy concerns.

Wednesday, Facebook said it plans to hire 3,000 more people to help monitor the millions of reports of alarming videos that it receives each week. That's in addition to the 4,500 people already doing so.

"Over the last few weeks, we've seen people hurting themselves and others on Facebook -- either live or in video posted later," Facebook CEO Mark Zuckerberg wrote in an online post. "It's heartbreaking, and I've been reflecting on how we can do better for our community."

Taking videos down is just one thing Facebook can do to help, Zuckerberg said Wednesday in a conference call to discuss first-quarter earnings.

"Last week, there (was) this case where someone was using Facebook Live to broadcast, or was thinking about suicide, and we saw that video and actually didn't take it down and helped to get in touch with law enforcement to use that live video to communicate with that person and help save their life," Zuckerberg said.

"So a lot of what we're trying to do is not just about taking the content down but also about helping people when they're in need on the platform, and we take that very, very seriously."